This application is related to and claims the priority of Japanese Patent Application No. 2000-128533, which was filed on Apr. 27, 2000.
1. Field of the Invention
The present invention generally relates to chain drives for land vehicles having at least one chain driven wheel. More particularly, the present invention relates to chain guides used in such drives.
2. Description of the Related Art
Recreational all terrain vehicles generally comprise a frame that is carried by at least one front wheel and a pair of rear wheels. The rear wheels typically are attached to the frame with a swing arm, which is connected to a rear portion of the frame and which is capable of pivotal movement relative to the frame about a generally horizontal axis. A shock absorber often is disposed between the swing arm and the frame to control movement of the swing arm during operation of the vehicle over rough terrain.
In some configurations, the rear wheels are driven by a final drive that includes a chain drive. The chain drive in such configurations comprises a drive pulley powered by an output shaft from an engine associated with the vehicle. A driven pulley is connected to the rear wheels and is driven by an endless roller chain that loops around the drive pulley and the driven pulley. Because a swing arm, which pivots up and down relative to a lower portion of the frame assembly, connects the rear wheels to the frame assembly, a chain guide can be provided to reduce slapping of the chain against the frame assembly or the swing arm.
Generally, at the pivot location, the swing arm connection comprises a tubular member that is journaled on a shaft with roller bearings. The bearings provide relatively free movement between the tubular member, which is associated with the swing arm, and the shaft, which is typically fixed to the frame assembly. Because of the size of the bearings, the tubular member generally has a large outside diameter due to the enlarged inside diameter required to accommodate the bearings.
To reduce the width of the associated vehicle, attempts have been made to reduce the length of the sleeve and shaft associated with the swing arm coupling. In addition, the drive pulley and the driven pulley have been moved laterally inward. In moving these components, the chain now passes over a portion of the swing arm coupling proximate the bearings. Because of this relative positioning, the chain guide needs to be positioned over this portion of the swing arm coupling as well. Unfortunately, due to the enlarged diameter of the tubular member, the chain guide is positioned higher than desirable. For instance, the elevated location of a guiding surface of the chain guide creates a rather abrupt angle in the chain at a forward end of the chain guide as the chain is loading onto the drive pulley. This disadvantageous angle can increase wear on the chain guide as the chain rubs over the end of the supporting surface. Such wear can rapidly decrease the life expectancy of the chain guide.
One proposed solution to this problem is to elevate the location of the drive pulley relative to the driven pulley. By elevating the drive pulley, the angle created during loading of the chain onto the drive pulley can be returned closer to 180 degrees such that no perceivable angle necessarily results. Elevating the drive pulley, however, results in an elevated center of gravity for the vehicle. Elevating the center of gravity of an all terrain vehicle is not desired. In fact, to the extent possible, one design goal of an all terrain vehicle is to lower the center of gravity. Accordingly, this proposed solution, while feasible, is less than desirable.
Another proposed solution is to lower the height of the pivot location and thereby lower the position of the chain guide. By lowering the pivot location, the angle of the chain during loading onto the drive pulley is decreased. Thus, wear on the chain guide end can be reduced; however, another design parameter for all terrain vehicles seeks to increase the clearance between the bottom of the vehicle and the ground. Lowering the pivot location of the rear swing arm, which forms a portion of the rear suspension system, thus disadvantageously reduces the clearance between the vehicle and the ground. Therefore, this solution, while again being workable, is less than desirable.
Accordingly, a chain guide and pivot location configuration is desired whereby the chain loading angle can be close to 180 degrees while also accommodating the components of the pivot and the chain guide.
Thus, one aspect of the present invention involves an all terrain vehicle comprising a frame assembly. At least one dirigible front wheel is attached to the frame assembly. A swing arm is pivotally mounted to the frame assembly. At least one rear wheel is connected to the swing arm. The swing arm comprises an outer lateral surface and a forward sleeve. The forward sleeve is journaled about a pivot shaft while the pivot shaft is connected to the frame assembly. At least one bearing member is disposed generally between the forward sleeve and the pivot shaft. An engine is mounted to the frame assembly with the engine comprising an output shaft. A drive pulley is powered by the output shaft and a driven pulley is connected to the at least one rear wheel. A flexible transmitter extends between the drive pulley and the driven pulley. A guide member is pivotally connected to the frame assembly proximate the forward sleeve of the swing arm. The guide member extends forward beyond at least a portion of the forward sleeve at a location generally laterally displaced from the at least one bearing member.
Another aspect of the present invention involves a guide member for an all terrain vehicle. The vehicle comprises a frame assembly and a swing arm pivotally connected to the frame assembly at a pivot joint. The swing arm comprises an outside lateral surface. The guide member comprises an upper guide surface with a retaining lip extending along at least a portion of the guide surface. The retaining lip extends upward from the guide surface. The guide member is adapted to be pivotally connected to the frame assembly and the guide member is adapted to be fixed to the outside lateral surface of the swing arm.
A further aspect of the present invention involves a guide member for use on an all terrain vehicle. The vehicle comprises a frame assembly. At least one dirigible front wheel is attached to the frame assembly and a swing arm is pivotally mounted to the frame assembly. At least one rear wheel is connected to the swing arm and the swing arm comprises an outer lateral surface and a forward sleeve. The forward sleeve is journaled about a pivot shaft and the pivot shaft is connected to the frame assembly. At least one bearing member is disposed generally between the forward sleeve and the pivot shaft. An engine is mounted to the frame assembly. The engine comprises an output shaft and a drive pulley is powered by the output shaft. A driven pulley is connected to the at least one rear wheel while a flexible transmitter extends between the drive pulley and the driven pulley. The guide member comprises a first portion adapted to be pivotally connected to the frame assembly proximate the forward sleeve of the swing arm such that the guide member extends forward beyond at least a portion of the forward sleeve at a location laterally displaced from the at least one bearing member.